A basic Michelson interferometer is sensitive to even very slight misalignment of optical elements. Such misalignment causes the two beam components to not overlap and therefore not produce a maximum fringe contrast when they move along equal path lengths. In interferometers utilized for spectral analysis, wedges can be utilized to vary the path length of different beam components, and also as the beamsplitter layer support to avoid channeling effects from beam components passing through the beamsplitter. However, where a wide beam passes through a wedge, different portions of the beam pass through different thicknesses of the glass or other wedge material, and the differences depend upon the exact rotational or lateral position of the wedge. Another problem encountered in the use of interferometers, is that polarization effects can occur, which are deleterious when there are reflections at a large angle to a mirror surface, such as more than 45.degree. from the normal, since differently polarized light may be reflected in different amounts in such reflections. These polarization effects reduce the maximum fringe contrast and hence the instrument efficiency. An interferometer system which was insensitive to slight tilting of its optical elements, was insensitive to rotation of wedges, was optical dispersion-phase-tunable across the wavefront without accurate wedge angle matching, avoided polarization effects, and introduced no channeling in the spectra, would be of considerable value.